1. Field of the Invention
The present invention relates to a network device that is used while connected to a network, particularly to a network device that can be put in a low-power consumption state.
2. Description of the Related Art
Recently, from a viewpoint of CO2 emission reduction, there is a social demand for low power consumption of an electric instrument. For example, in a network device connected to a network such as a LAN, there is known a network device, in which only a Network Interface Controller (hereinafter referred to as “NIC”) connected directly to the network is operated while power supplies of a CPU and a hard disk are stopped during standby, thereby realizing power saving. An example of the network device is a network printer that transitions to the low-power consumption state, in which the supply of the power to a printer controller, a printer engine, and the like are stopped during standby. In a configuration of such a network printer, only the NIC is operated to wait for print data transmitted from an external host computer (hereinafter also referred to as “communication terminal”) when the network printer is in the low-power consumption state, and the printer controller and the like are returned from the low-power consumption state to a normal power state when the print data is received.
In this case, print data processing cannot be performed when the printer controller and the like are being started up. In order not to receive the print data during the start-up, there is considered a configuration in which a session is not established with the communication terminal when starting up the printer controller and the like. However, with such a configuration, the communication terminal repeatedly transmits a session establishment request at predetermined time intervals. Therefore, even if the start-up of the printer controller and the like is ended to be able to establish the session with the communication terminal, the session cannot be established until the communication terminal transmits the session establishment request again. Therefore, the receive processing and the print data processing cannot be started although the print data processing can be performed, which causes a problem in that the start of the processing is delayed. Further, when the session is timed out because a response is not received for a predetermined time or more, a determination is made that the session cannot be established, to possibly generate an error on the communication terminal side.
In order to solve the above problems, for example, there is a multifunction peripheral that prohibits the data transmission by continuously transmitting a denial signal (NACK) to a source (communication terminal) of a print request until a confirmation that a PDL board returns to an operable state can be obtained. In the multifunction peripheral, when a main board receives a print request from a terminal device through an interface in an energy-saving mode, a function of a power supply circuit is activated to start the return to the normal mode from the energy-saving mode through a standby mode. At the same time, a control unit of the main board monitors the state of the PDL board, and the control unit transmits the denial signal (NACK) to the source of the print request to prohibit the terminal device from performing the data transmission until a confirmation that the return of the PDL board to the operable state is completed can be obtained. When the completion of the return is confirmed, a signal (ACK) for permitting the print request is transmitted to the source to permit the data transmission.
However, in a network communication control, a protocol that can use the signal NACK is limited to a specific protocol (such as an LPR protocol (Line Printer daemon protocol)). Moreover, even if the LPR protocol is used, the signal NACK is ignored and will not-function effectively when a host computer adopts Windows (registered trademark, hereinafter the same) as an Operating System (OS). Accordingly, the control method performed by the above multifunction peripheral does not function effectively for the communication terminal in which a protocol except the LPR protocol is used and the communication terminal in which Windows is adopted as the OS. That is, —the conventional network device has poor versatility.